1. Field of the Invention
The present invention relates to data signal transmitting method and data signal receiving method in a wireless communication system, and more particularly, to a method of transmitting and receiving data signal in a wireless communication system by changing a transmission speed and a payload size included in the data signal according to an operation environment.
2. Description of the Related Art
In a wireless sensor network (WSN), since each sensor device uses a limited power source, such as a battery, a communication technology reducing power consumption is indispensible. For example, in IEEE 802.15.4 that is a type of WSN medium access control (MAC) method, power consumption is reduced by enabling communication devices in a system to transmit and receive data only in an active interval and stopping the communication devices from operating in an idle or inactive interval, by using a beacon-enabled mode that periodically uses a transmission frame including a synchronizing signal transmitting interval, a transmitting interval, and an idle interval. Here, a beacon frame that is a network synchronizing signal periodically transmitted for synchronization of transmitting periods between the communication devices in the WSN includes information of a transmitting interval and idle interval, scheduling information for assigning an independent resource to a communication device, and information notifying a communication device that there is a packet to be transmitted.
When a plurality of wireless communication systems of different types or same type, which share the same frequency band, exist, a direct sequence spread spectrum (DSSS) system reduces an effect of an interference signal within a band via a spread spectrum technique. For example, in IEEE 802.15.4 that is a type of the DSSS system, a transmission signal is spread and transmitted so as to obtain a processing gain with respect to a narrowband interference signal. However, a performance of IEEE 802.15.4 DSSS is not largely effective when a frequency static interference signal that causes interference for a relatively long interval of time in a wide frequency band, such as a wireless local area network (WLAN), exists. In detail, in the beacon-enabled mode of IEEE 802.15.4, since the beacon frame is simply periodically transmitted, when an interference signal exists in a channel being used, a transmission performance of the beacon frame is remarkably deteriorated and thus severe power consumption and performance deterioration are induced due to signal transmission delays and repeated attempts to receive a synchronization signal by the communication devices. Also, when the communication device is unable to continuously receive a beacon frame, the communication device may change to an orphan device by losing synchronization with a main communication device (hereinafter, referred to as a coordinator) of a system, and a long time is taken and a large amount of power is consumed during a re-joining process for re-connecting to a network. Thus, when same or different type interference signals exist, the beacon-enabled mode of IEEE 802.15.4 not only deteriorates network connectivity, but also seriously deteriorates a data transmission performance.
Accordingly, techniques for increasing network connectivity and a data transmission performance in an environment having interference in a channel being used have been suggested. For example, various techniques, such as a deferred beacon method (DBM) of IEEE 802.15.4e MAC enhancement for reliably transmitting a control message in an environment having interference in a channel being used, a technique for increasing a data transmission performance by changing a transmission speed according to channel environments (hereinafter, referred to as dynamic rate adaption and control for energy reduction (DRACER)), and a technique for increasing a data transmission performance by varying a packet size according to channel environments (hereinafter, referred to as white-space aware frame adaption (WISE), have been suggested. However, since most techniques do not consider various operation environments that may occur in an actual environment, a network performance may deteriorate, and in addition, such most techniques do not consider transmission of control messages and data signals in overall, and thus performance improvement is inadequate.
For example, since the DBM depends upon a channel sensing result of a coordinator, a performance may largely deteriorate in an environment (for example, a hidden node environment) in which an interference signal effect is high only to some communication devices. Also, when a packet error occurs, the DRACER reduces a signal transmission speed by increasing a DSSS code rate by determining that a channel state is deteriorated, but if the packet error is generated by an interference signal, a transmission time of an actual signal is increased since a packet size is fixed and the signal transmission speed is reduced, and thus the DRACER may become more vulnerable to the interference signal and a performance may rather deteriorate. Also, in the WISE, characteristics of an interference signal in the same channel are recognized and a payload size is determined to split and transmit data, but since the WISE does not consider variation of a transmission speed according to channel states, and thus performance improvement is insignificant.